Question

What is the half-life of a zero order reaction that takes 25 minutes for 80% completion?

• A. 150.25 seconds
• B. 937.50 seconds
• C. 950.50 seconds
• D. 156.25 seconds

Hint:

In Zero Order, the reaction proceeds at a steady pace. Half-life is proportional to initial concentration.

Answer 1

The Correct Option is B

Step 1: Concept
For a zero-order reaction, the rate is constant, so $x = kt$ (where $x$ is amount reacted).

Step 2: Meaning
80% completion in 25 min means $0.8[A]_0 = k \times 25$. This gives $k = 0.8[A]_0 / 25$.

Step 3: Analysis
The half-life ($t_{1/2}$) for zero order is $[A]_0 / 2k$. Substituting $k$: $t_{1/2} = [A]_0 / (2 \times 0.8[A]_0 / 25) = 25 / 1.6 = 15.625$ minutes.

Step 4: Conclusion
Convert to seconds: $15.625 \times 60 = 937.5$ seconds. Final Answer: (B)